*{
    margin: 0;
    padding: 0;
}

body,html{
    width: 100%;
    height: 100%;
}
.nav-box{
    width: 200px;
    background: rgb(50, 65, 87);
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    overflow-y: auto;
    padding-top: 40px;
}
.nav-box ul{
    list-style: none;
    line-height: 50px;
    font-size: 14px;
    color: #ddd;
}
.nav-box ul .nav-block{
    padding-left: 10px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: flex-start;
    flex-wrap: wrap;
    position: relative;
    font-size:20px;
    padding-top: 10px;
    margin-top: 20px;
}
.nav-box ul .nav-block:hover{
    color: #fff;
    background: rgb(40, 52, 70);
}
.nav-box ul li i{
    display: inline-block;
    width: 40px;
    height: 40px;
}
.nav-box ul li i.arrow{
    position: absolute;
    top: 5px;
    right: 5px;
}
.nav-block a:link{
color: #fff;
}


.nav-box .nav-block.on i.arrow{
    transform: rotate(0deg);
}
.nav-box .nav-two{
    display: block;
    width: 100%;
    font-size: 13px;
    line-height: 45px;
    display: none;
}
.nav-block.on+ul.nav-two{
    display: block;
}
.nav-box .nav-two li{

    padding-left: 38px;
    cursor: pointer;
    counter-reset: write;
    color: #fff;
}
.nav-two a:link{
    color: #fff;

}
.nav-box .nav-two li:hover{
    background: rgb(40, 52, 70);
}
.header{
    border: solid 1px black;
    width: 1800px;
    height: 60px;
    background: green;
    
}
.header h1{
    text-align: center ;
    font-size: 50px;
    font-family: 隶书;
    letter-spacing: 20px;
    position: relative;
}
.return {
    width:600 px;
    height: 30px;
    position: absolute;
    top: 20px;
    left: 1550px;
    font-size: 30px;
}
.return a{
    text-decoration: none;
}    
:root {
    --primary-color: #3498db;
    --danger-color: #e74c3c;
    --success-color: #2ecc71;
    --text-color: #2c3e50;
    --bg-color: #f8f9fa;
}
body {
    font-family: 'Segoe UI', system-ui;
    background-color: var(--bg-color);
}
/* 安全设置容器 */
.security-container {
    max-width: 700px;
    height: 450px;
    margin: 80px auto;
    padding: 50px;
    background: light-dark;
    border-radius: 20px;
    box-shadow: 15px 18px 30px rgba(0,0,0,0.2);
}
.security-title {
    color: var(--text-color);
    border-bottom: 2px solid var(--primary-color);
    padding-bottom: 0.5rem;
    margin-bottom: 2rem;
    font-size: 35px;
}
/* 密码输入组 */
.password-group {
    position: relative;
    margin-bottom: 2.5rem;
}
.password-input {
    width: 600px;;
    padding: 15px 45px 12px 15px;
    border: 2px solid #e0e0e0;
    border-radius: 10px;
    transition: border-color 0.3s;
}
.password-input:focus {
    border-color: var(--primary-color);
    outline: none;
}
/* 显示密码切换 */
.toggle-password {
    position: absolute;
    right: 50px;
    top: 25px;
    transform: translateY(-50%);
    cursor: pointer;
    color: #95a5a6;
}
/* 密码强度指示器 */
.strength-meter {
    width: 670px;
    height: 4px;
    background: #eee;
    margin-top: 8px;
    border-radius: 2px;
    overflow: hidden;
}
.strength-fill {
    width: 0;
    height: 100%;
    transition: all 0.3s;
}
/* 验证提示 */
.validation-message {
    font-size: 0.85rem;
    margin-top: 6px;
    display: none;
}
/* 提交按钮 */
.submit-btn {
    background: var(--primary-color);
    color: white;
    padding: 12px 30px;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: opacity 0.3s;
    width: 100%;
    height: 50px;
    font-weight: 500;
    font-size: 20px;
}
.submit-btn:hover {
    opacity: 0.9;
}
/* 响应式设计 */
@media (max-width: 768px) {
    .security-container {
        margin: 1rem;
        padding: 1.5rem;
    }
}
